1. Field of the Invention
This invention relates to a method of and apparatus for controlling the thickness of a coating applied to moving sheet material and, more particularly, to the method of and apparatus for controlling the thickness of a coating applied to the upper side of fabric moving between two points, the lower side of the fabric being unsupported therebetween.
2. Description of the Prior Art
U.S. Pat. No. 3,007,205 teaches a process of forming a cured foam rubber layer having a textile fabric embedded therein and shows an apparatus for carrying out this process. The fabric to be embedded in the foam layer enters a bank of foam at an angle to the horizontal, passes under a rotating guide roll positioned within the bank of foam, continues through the foam, and passes between a rotating doctor roll and a rotating endless belt supported thereunder by a supporting plate, the collection of the doctor roll and endless belt and supporting plate thereunder controlling the thickness of the foam rubber layer with the fabric embedded therein. In the method and apparatus of the invention described herein, the fabric to have a coating of controlled thickness on its one side does not enter into a bank of coating material at an angle to the horizontal and, in fact, does not even enter into a bank of coating material, does pass under a device the equivalent of a guide roll but such device is not positioned in a bank of coating material, does not continue through a bank of coating material but passes under a convenient reservoir of such material, and does not have the thickness of the coating material applied controlled while passing between a doctor roll and an endless belt supported thereunder by a plate but has the thickness of the coating material controlled by a thickness-controlling device positioned on the side of the fabric being coated while the opposite side of the fabric is unsupported thereunder.
U.S. Pat. No. 3,385,751 teaches a method of making tufted pile carpet wherein part of the method includes the forming of a plastic foam sheet with a reinforcing layer disposed within the sheet. The patent also shows the apparatus for carrying out this portion of the method. The reinforcing material to be disposed within the plastic foam sheet passes under a foam mixing head which dispenses foam onto a carrier belt, enters into and continues through the dispensed foam on the carrier belt, and passes between a carrier belt on the bottom and a cover belt on the top, both of which are backed up by metering rolls to control the thickness of the foam with the reinforcing layer of material therein. In the method and apparatus of the invention described herein, the fabric, to have a coating applied to its one side, the thickness of the coating being controlled, passes under a device which functions similarly to the bottom of the mixing head of the patent, but does not enter into the coating material immediately after this point or at any subsequent point, does therefore not continue to travel within the coating material but travels with the coating material on its one side, and does not have the thickness of the coating controlled by a pair of metering rolls, one above the coating material and one under the fabric, but has the thickness of the coating material controlled by a controlling device positioned above the coating with no supporting means under the fabric.